How high do the subclavian arteries ascend into the neck? A population study using magnetic resonance imaging

Background. The relationship between the larynx and the subdavian arteries was studied in a series of magnetic resonance images (MRIs) from 50 patients without neck pathology. Methods. The vertical distances of the excursion of the subdavian arteries into the neck was measured, as was the distance from the cricoid cartilage to the highest point of this excursion. Statistical analysis allows the probability of any given cricoid-subclavian distance occurring in the population to be estimated. Results. The mean (SD) excursion of the right subdavian artery above the clavicle was 10.4 (11.4) mm. The mean (SD) distance from the cricoid cartilage to the right subdavian artery was 30.6 (14.3) mm, and the data showed a high degree of variance. There was a linear relationship between neck length and cricoid-subclavian distance (r=0.58), which explained some of the variance in the latter, but there was also wide individual variance, which was independent of this regression. Conclusions. When performing a percutaneous tracheostomy, a 'safe' distance between the incision site and subdavian artery cannot be assumed or reliably predicted from the neck length.